.netcore2.1 JS-SDK 从后台获取微信签名，实现自定义分享标题、描述、图片

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最近项目移动端需要实现微信自定义分享功能，包含分享自定义标题、描述等。

首先到公众号的后台，功能设置里面，添加将要被分享的域名，如图

后端签名算法实现，参考腾讯开发者文档https://mp.weixin.qq.com/wiki?t=resource/res_main&id=mp1421141115

jsapi_ticket

生成签名之前必须先了解一下jsapi_ticket，jsapi_ticket是公众号用于调用微信JS接口的临时票据。正常情况下，jsapi_ticket的有效期为7200秒，通过access_token来获取。由于获取jsapi_ticket的api调用次数非常有限，频繁刷新jsapi_ticket会导致api调用受限，影响自身业务，开发者必须在自己的服务全局缓存jsapi_ticket 。

生成签名步骤，获取AccessToken-》获取JsApiTicket-》生成签名

appsettings配置文件添加配置

"Api": {
"JSJDKBaseApi": "https://api.weixin.qq.com/cgi-bin"
},
"JSJDK": {
"AppId": "***",
"Secret": "****"
}

创建签名公用类

public class JSSDKSignHelper
{
private static AccessTokenResponse singleAccessToken; private string _tencentApi { get; set; }
private string _appid { get; set; }
private string _appSecret { get; set; } public JSSDKSignHelper(IConfiguration config)
{ _tencentApi = config["Api:JSJDKBaseApi"];
_appid = config["JSJDK:AppId"];
_appSecret = config["JSJDK:Secret"];
} public string GetAccessTokenSingle(out bool isNewObj)
{
isNewObj = false;
if (singleAccessToken != null && (singleAccessToken.expire_out > DateTime.Now.AddHours()))
{
return singleAccessToken.access_token;
}
else
{
var response = GetAccessToken();
if (response.errcode == )
{
response.expire_out = DateTime.Now.AddHours(expireHour);
singleAccessToken = response;
isNewObj = true;
return response?.access_token;
}
}
return null;
} /// <summary>
/// 获取access_token
/// </summary>
/// <returns></returns>
private AccessTokenResponse GetAccessToken()
{ string url = _tencentApi + "/token?grant_type=client_credential&appid=" + _appid + "&secret=" + _appSecret;
var response = ApiClient.GetJson<AccessTokenResponse>(url);
return response;
} /// <summary>
/// 获取JsApiTicket
/// </summary>
/// <param name="accessToken"></param>
/// <returns></returns>
public string GetJsApiTicket(string accessToken)
{
if (string.IsNullOrWhiteSpace(accessToken))
{
return null;
}
string url = _tencentApi + $"/ticket/getticket?type=jsapi&access_token={accessToken}"; var response = ApiClient.GetJson<AccessTicketResponse>(url); return response?.ticket;
} /// <summary>
/// 获取签名
/// </summary>
/// <param name="jsapi_ticket"></param>
/// <param name="noncestr">随机字符串(必须与wx.config中的nonceStr相同)</param>
/// <param name="timestamp">时间戳(必须与wx.config中的timestamp相同)</param>
/// <param name="url">当前网页的URL，不包含#及其后面部分(必须是调用JS接口页面的完整URL)</param>
/// <returns></returns>
public string GetSignature(string jsapi_ticket, string noncestr, string timestamp, string url)
{
if (string.IsNullOrEmpty(jsapi_ticket) || string.IsNullOrEmpty(noncestr) || string.IsNullOrEmpty(timestamp) || string.IsNullOrEmpty(url))
return null;
var string1Builder = new StringBuilder();
string1Builder.Append("jsapi_ticket=").Append(jsapi_ticket).Append("&")
.Append("noncestr=").Append(noncestr).Append("&")
.Append("timestamp=").Append(timestamp).Append("&")
.Append("url=").Append(url.IndexOf("#") >= ? url.Substring(, url.IndexOf("#")) : url);
return Sha1Sign(string1Builder.ToString());
} /// <summary>
/// Sha1加密签名
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public string Sha1Sign(string str)
{
SHA1 sha1 = new SHA1CryptoServiceProvider();
byte[] bytes_sha1_in = System.Text.UTF8Encoding.Default.GetBytes(str);
byte[] bytes_sha1_out = sha1.ComputeHash(bytes_sha1_in);
string signature = BitConverter.ToString(bytes_sha1_out);
signature = signature.Replace("-", "").ToLower();
return signature;
} }

签名定义的Model

public class AccessTokenResponse: BaseResponse
{
/// <summary>
/// 返回access_token值，有效期7200秒
/// </summary>
public string access_token { get; set; }
/// <summary>
/// 过期时间，单位小时
/// </summary>
public DateTime expire_out { get; set; } } public class AccessTicketResponse : BaseResponse
{
/// <summary>
/// 返回Ticket票据，有效期7200秒
/// </summary>
public string ticket { get; set; } }
public class BaseResponse
{
/// <summary>
/// 过期时间，单位秒
/// </summary>
public string expire_in { get; set; }
/// <summary>
/// 错误代码
/// </summary>
public Int32 errcode { get; set; }
/// <summary>
/// 错误信息描述
/// </summary>
public string errmsg { get; set; }
}

创建生成签名的时间戳和随机串

/// <summary>
/// 获取微信JS-JDK时间戳
/// </summary>
/// <returns></returns>
public static string GetTimeStamp()
{
TimeSpan ts = DateTime.UtcNow - new DateTime(, , , , , ); return Convert.ToInt64(ts.TotalSeconds).ToString();
} /// <summary>
/// JS-JDK 创建随机字符串
/// </summary>
/// <returns></returns>
public static string CreatenNonce_str()
{
Random r = new Random();
var sb = new StringBuilder();
var length = strs.Length;
for (int i = ; i < ; i++)
{
sb.Append(strs[r.Next(length - )]);
}
return sb.ToString();
}

Action中实际调用

[HttpPost]
[Route("GetSignature")]
public string GetSignature(string url= "http://www.sina.cn/")
{
try
{
if (string.IsNullOrEmpty(url)) return "url不能为空";
string _jsTicket = null, _signature = null;
string _accessToken = _jsSignHelper.GetAccessTokenSingle(out bool isNewObj);
WxConfigModel model = new WxConfigModel();
model.AppId = appId;
model.TimeStamp = MyUtil.GetTimeStamp();
model.NonceStr = MyUtil.CreatenNonce_str();
if (isNewObj|| _wxConfigModel.Signature==null)
{ _jsTicket = _jsSignHelper.GetJsApiTicket(_accessToken);
_signature = _jsSignHelper.GetSignature(_jsTicket, model.NonceStr, model.TimeStamp, url);
model.jsTicket = _jsTicket;
model.Signature = _signature;
_wxConfigModel = model;
}
return JsonConvert.SerializeObject(model);
}
catch (Exception ex)
{
throw ex;
}
}